What controls variation in carbon use efficiency among Amazonian tropical forests?

Why do some forests produce biomass more efficiently than others? Variations in Carbon Use Efficiency (CUE: total Net Primary Production (NPP)/ Gross Primary Production (GPP)) may be due to changes in wood residence time (Biomass/NPPwood), temperature, or soil nutrient status. We tested these hypotheses in 14, one ha plots across Amazonian and Andean forests where we measured most key components of net primary production (NPP: wood, fine roots, and leaves) and autotrophic respiration (Ra; wood, rhizosphere, and leaf respiration). We found that lower fertility sites were less efficient at producing biomass and had higher rhizosphere respiration, indicating increased carbon allocation to belowground components. We then compared wood respiration to wood growth and rhizosphere respiration to fine root growth and found that forests with residence times <40 yrs had significantly lower maintenance respiration for both wood and fine roots than forests with residence times >40 yrs. A comparison of rhizosphere respiration to fine root growth showed that rhizosphere growth respiration was significantly greater at low fertility sites. Overall, we found that Amazonian forests produce biomass less efficiently in stands with residence times >40 yrs and in stands with lower fertility, but changes to long-term mean annual temperatures do not impact CUE.

Goldsmith, Gregory R.Chapman University,Paul Scherrer Institute (author)
Raab, NicolasUniversity of Oxford (author)
Girardin, Cecile A. J.University of Oxford (author)
Farfan Amezquita, FilioNational University of Saint Anthony the Abbot in Cuzco (author)
Huaraca Huasco, WalterUniversity of Oxford,National University of Saint Anthony the Abbot in Cuzco (author)
Silva Espejo, Javier E.Universidad de La Serena (author)
Araujo-Murakami, AlejandroGabriel René Moreno Autonomous University (author)
da Costa, Antonio C. L.Federal University of Pará (author)
Rocha, WanderleyAmazon Environmental Research Institute (IPAM) (author)
Galbraith, DavidUniversity of Leeds (author)
Meir, PatrickAustralian National University,University of Edinburgh (author)
Metcalfe, Dan B.Lund University,Lunds universitet,Institutionen för naturgeografi och ekosystemvetenskap,Naturvetenskapliga fakulteten,Dept of Physical Geography and Ecosystem Science,Faculty of Science(Swepub:lu)nate-dma (author)
Malhi, YadvinderUniversity of Oxford (author)
Northern Arizona UniversityChapman University (creator_code:org_t)

By the author/editor: Doughty, Christo ...; Goldsmith, Grego ...; Raab, Nicolas; Girardin, Cecile ...; Farfan Amezquita ...; Huaraca Huasco, ...; show more...; Silva Espejo, Ja ...; Araujo-Murakami, ...; da Costa, Antoni ...; Rocha, Wanderley; Galbraith, David; Meir, Patrick; Metcalfe, Dan B.; Malhi, Yadvinder; show less...

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